Support is requested for a Keystone Symposia meeting entitled Innate Immunity and Determinants of Microbial Pathogenesis, organized by Robert L. Modlin, Jenny P.Y. Ting and Foo Y. Liew. The meeting will be held in Olympic Valley, California from April 19-24, 2015. In 2000, Keystone Symposia held a meeting on Determinants of Immune Defense Against Microbial Infections that received outstanding reviews. At the time, the meeting fulfilled an unmet scientific need - a small interactive gathering for those interested in microbial immunology from the perspective of gaining insight into basic immune mechanisms, understanding microbial pathogenesis and developing preventative and therapeutic interventions. Today, this topic is even more timely given the emergence of drug resistant organisms, the advances in immunology, the insights gained from understanding the normal and disease microbiome, and the rapid technologic advances including high throughput sequencing and robotics. The 2015 meeting will focus on innate and adaptive immunity to microbial infections. Microbial infections pose major health problems worldwide, but also represent extraordinary models to study immune regulation. Important advances in immunology have been made in recent years and have led to a new understanding of host-pathogen interactions. This Keystone Symposia meeting will explore the interaction of the innate and adaptive immune response in the host defense against microbial infection. Topics include: Innate Immunity, Innate Immune Sensing and Consequences in Microbial Infection, Innate Immunity in Inflammation and Disease, Adaptive Immunity, Regulation of Immune Responses, Immune Mechanisms in Inflammation and Infection, Intervention/Vaccines, and Targets for Immunotherapy. This meeting aims to bring together immunologists who study basic mechanisms and those that study infectious agents to formulate new strategies to control some of the world's most deadly diseases. Opportunities for interdisciplinary interactions will be significantly enhanced by the concurrent meeting on Mechanisms of Pro-Inflammatory Diseases, which will share a keynote address and three plenary sessions with this meeting.